This invention pertains to can making and more particularly to means for sealing their seam joints.
As shown, for instance, in U.S. Pat. No. 3,000,338 issued in my name, can bodies to be side-seam soldered are often advanced in a row to and through a soldering station by means of feed dogs uniformly spaced along an endless chain and engageable with a respective trailing edge of the bodies. Though closely spaced, the aligned can bodies are not contiguous. Since the solder is preferably to be flowed or deposited continuously from outside of the bodies by jet or other suitable applicator means, solder can flow into the gap between adjacent bodies and project into their leading and/or trailing end portions unless protective measures are taken. One approach to prohibiting such entry of the unwanted molten solder is to employ an internal shield or roll biased by a counterweight or otherwise for engagement with the inside of the cans opposite to the locality of solder application. An arrangement of this type is disclosed, for example, in U.S. Pat. No. 3,371,837 issued in my name.
It is a common practice, however, to apply prior to side-seam soldering an internal protective spray or coating which may cover the entire can interior protectively (or for the protection of foodstuff to be contained), and to apply internally along the side seam to which solder is to be directed only a band of suitable lacquer of the like. This band is termed a "pre-stripe". It may still be wet or not yet toughened when the can body is to be soldered. In the circumstances, it is important that the pre-stripe, or any internal coating adjacent to the side seam, not be impaired or its integrity disturbed either by influx of excess solder or by a shielding device such as a roll used to plug the end gaps between successive side seams.